Housing for light-sensitive devices



Jan. 7, 1964 w. LUFT HOUSING FOR LIGHT-SENSITIVE DEVICES Filed April 26, 1961 INVENTOR. 1445/94 53 & 0P

43 new E/ r, F255 54 .9 {ha /v United States Patent 3,ll7,25 HGUSHQG FOR LIGHI-lENSITIVE DEVICES Werner Luit, Torrance, Calitl, assignor to International Rectifier Corporation, El Segundo, Calif., 21 corporation of California Filed Apr. 26, 196i, Ser. No. 105,620 Claims. (Cl. 338-19) My invention relates to a novel hermetically sealed housing construction for light-sensitive devices, and more specifically relates to a cylindrical cross-section transparent housing for cadmium-sulphide photoconductive elements.

Cadmium-sulphide photoconductive elements are well known to the art. It is often necessary to package such devices to protect them from adverse influence of atmosphere and possible mechanical abrasion. Moreover, the package must be either fully or partially transparent or translucent, and must expose a maximum amount of the light-sensitive surface of the device housed therein. Furthermore, the housing should be as sturdy as possible and lend itself to inexpensive mass production manufacturing techniques.

In accordance with the present invention, a cadmiumsulphide photoconductive layer is deposited on a relatively flexible backing material in the usual manner, although a rigid backing material could be used. By way of example, a backing material of mica, having an elongated cadmium-sulphide layer and conductive layers deposited thereon in the usual manner would be preferred.

The elongated strip of material so formed is then provided with terminals on opposite sides of the cadmiumsulphide layer, and the strip of material is then curved or bent and inserted in a transparent cylinder which could be of glass, and is slightly longer than the strip of photosensitive material. The terminals on the strip extend beyond either end of the tube, and the tube is thereafter filled with a transparent epoxy resin such as Hysol 6063 with B-Hardener respectively :1 part by weight, whereby the sheet of material bearing the cadmium-sulphide photo-sensitive layer is rigidly secured within the tube. The terminals of the strip, of course, extend beyond either end of the cylindrical tube for receiving electrical connections to the device.

If desired, the terminals can be embedded in a glass plug which may be fitted tightly within the tube, and sealed to the tube by appropriate glass-to-glass sealing techniques. In such a case, the tube can be filled with a fluid to facilitate heat transfer from the light-sensitive device to the external glass tube such as a silicon oil which is captured within the tube by the seals associated with the end electrodes.

Accordingly, a primary object of this invention is to provide a novel housing for cadmium-sulphide photoconducti-ve elements.

Another object of this invention is to provide a transparent housing for cadmium-sulphide photo-sensitive elements wherein the photo-conductive elements are rolled into a cylindrical shape, and the housing is formed of a glass tube which cooperates with the shape of the cylindrical elements.

A further object of this invention is to provide a novel inexpensive housing for cadmium-sulphide photo-conductive elements.

Yet another object of this invention is to provide a novel transparent housing for photo-sensitive devices which is at least partially transparent or translucent, and protects the photo-sensitive elements from mechanical abrasion and from the eifects of the external atmosphere.

A still further object of this invention is to provide a novel housing for photo-sensitive elements which may be economically produced and lends itself to mass production techniques.

These and other objects of my invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 shows a strip of material having a cadmiumsulphide layer with an electrically conductive collector pattern deposited thereon.

FIGURE 2 illustrates the manner in which the strip of FIGURE 1 is curved into a cylindrical shape, and has electrodes attached at either end.

FIGURE 3 illustrates the manner in which the strip of FIGURE 2 is contained within a cylindrical glass tube housing and is filled with a transparent epoxy.

FIGURE 4 illustrates the manner in which one of the terminals of the device may be provided with a glass bead therearound and has an extending cylindrical body receiving the cylindrical photo-sensitive strip.

FIGURE 5 illustrates the manner in which a terminal of FIGURE 4 is contained within a glass tube and connected to a photo-sensitive strip.

FIGURE 6 is a partially perspective view of the end of a housing formed in the manner shown in FIGURE 5.

FIGURE 7 illustrates a modification of the embodiment of FIGURES 4, 5 and 6 when the terminal is rectangular rather than circular.

FIGURE 8 illustrates the manner in which the support tube has only a single open end with both terminals of the device extending outwardly of this single open end.

Referring now to FIGURE 1, I have shown an elongated strip 9 of material which may be formed of a backing of mica material which is relatively flexible and has deposited thereon an elongated layer ll) of cadmiumsulphide which has superimposed two independent electrically conductive patterns 11 and 12. The rating is a function of the average spacing between 11 and 12.

In accordance with the well known application of cadmium-sulphide devices, conductive collectors 11 and 12 serve as terminals for the device where the current passed between collectors is dependent upon the resistance of the exposed area of layer It) of cadmium-sulphide which, in turn, is dependent upon the light intensity incident upon the exposed area of layer It).

As illustrated in FIGURE 2, a first terminal 13 is electrically and mechanically secured to conductive layer 12 by rivet 14 which passes through strip 9 and electrically engages conductive surface 12. If desired, the terminal 13 could be connected to surface layer 12 in any other desired manner as by forming conductive eyelets in the manner illustrated in copending application Serial No. 105,704, filed April 26, 1961 in the name of Abraham B. Leshen, entitled Housing Construction for Light-Sensitive Devices, and assigned to the assignee of the present invention.

In a similar manner, terminal 15 is secured at the other end of the cylinder defined by the light-sensitive device and to conductive layer 11.

The cylinder is then rolled into a cylindrical shape and, as shown in FIGURE 3, is inserted into a glass tube 16 which has a height slightly longer than the length of the strip of FIGURE 2, but less than the length between the ends of terminals 13 and 15, so that the terminals 13 and $15 extend beyond the ends of tube 16.

While tube 16 may be a glass tube, it will be apparent that it can be of any transparent, sturdy material such as an appropriate plastic. Furthermore, the cross-sectional shape of tube 16 and of rolled strip 9 of FIGURE 2 conform to one another. Thus, while I have shown both the strip and the tube to be circular in shape, it will be apparent that they could be of other similar shapes such as rectangular, square, oval and the like.

Moreover, the power dissipation ability of the device is a function of the length of the tube.

After the photo-sensitive device is inserted in tube 16, the tube is filled with a transparent epoxy of any readily available type such as l-lysol 60-63 with B-l-lardcner respectively 10:1 part by weight. When the epoxy hardens, the circular photo-sensitive device will be rigidly secured within tube 16. Whatever epoxy appears between the outwardly disposed. photo-sensitive face of tube 16 will not interfere with incident radiation passing through. tube 16 and directed toward the photo-sensitive face of the device, since it is transparent.

It will be apparent that the device of FIGURE 3 will lend itself to exceedingly simple manufacturing techniques, and that the housing construction involves a minimum of expense. Moreover, the housing will completely protect the photo-sensitive device from external atmospheric influences and provides protection for the photo-sensitive device from mechanical scratching, or corrosion due to atmospheric conditions between terminals 1'3 and 15 and their respective conductive layers 12 and 11 respectively. Furthermore, as heat is generated in the light-sensitive region lid, there will be effective removal of such heat through terminals 13 and E5 and outwardly to external heat sinks, as Well as through the epoxy.

A second embodiment of the invention is set forth in FIGURES 4 through 6. in this embodiment, a cadmium-sulphite cell similar to that of FlGURES '1 and 2 and which could have a mica backing is again formed in a semicircle, and is to be contained ,Wli l'lln the glass tube 16, shown in FIGURES 5 and 6. in the case of this embodiment, the terminals for each end of the glass tube are identical to one another, one such terminal being shown in FIGURE 4 as terminal 17.

Terminal 1? is comprised of a circular cross-section conductive number 18 of relatively large cross-section to serve as an effective heat conductor, and has a relatively larger symmetrical cross-section at its inner end. By enlarging the terminal surface in this manner, there is improved heat transfer from strip 9 to terminal 18 so that the power rating of the device may be increased. Enlarged portion 518a is contoured to conform to the inner curvature of the light-sensitive device 9 whereby the terminal end 1311 can receive conductive fasteners which pass through the backing of the photosensitive device and terminate on the conductive surface such as conducive surface 12 of FIGURE 1 to electrically connect conductive surface 12 to termina Such fasteners can, for example, be accepted by tapped holes 19 and 2t) in terminal portion 180 in FIGURES 4 and 5.

If desired, the novel eyelet-type of terminal disclosed in the above noted copending application Serial No. 105,704, filed Apri 126, 1961, could be used to provide electrical connection between terminal porhion 18a and conductive surface 12. Clearly, the terminal at the lower end of tube lb will be formed in an identical manner, but will be electrically secured to conductive layer ll of the sheet of FIGURE 1.

A glass head 21 or glass button is then secured to terminal portion 18 as shown, by appropriate 111etaltoglass seal-forming techniques where the curvature of button 21 conforms to; the curvature of the ends of tube 16. Preferably, the buttons 21 of the upper and lower terminals will have a slightly smaller diameter than the internal diameter of the tube for permitting ease of asesmbly. That is, in assembling the device, the upper and lower terminals are first secured to the strip of FiGURE 2, and the button 21 at the bottom of the cylindrical sheet is inserted in the top of the tube, and the tube is then inserted completely Wi hn tube to. This requires that at least the lower button 21 be of a sufiicient diameter to pass througi the tube until it reaches the bottom of the tube, and the upper button 2} reaches the top of the tube. Thereafter, the glass tube 16 is fused to the buttons 21 4 by appropriately heating their interfaces in the usual manner, whereby the tube 16 is hermetically sealed.

If desired, the tube can be filled with an appropriate heat transfer fluid such as a silicone oil to promote additional heat transfer between the light-sensitive device of FIGURE 1 and the external tube 3 While in FIGURES 4, 5 and 6 l have shown the extending terminal 13 having a circular cross-section, it is apparent that any des red cross-section could be used. By way of example, and as shown in FKGURE 7, the extending term nal can have the rectangular shape shown as terminal 33 which can also serve for orientation of the device.

A third embodiment of the invention is set forth in FIGURE 8 for the case of a tube havin only one open end, the lower end of the tube being closed. in such a case, a glass button 22. may be used which receives two elongated terminals of conductive material 23 and The terminal 23 will be electrically connected to conduotive layer l2 as by a rivet which extends through the strip, while electrode 24 is electrically connected to layer ll by rivet 26 which extends through the strip in the usual manner.

Although I have described preferred embodiments of my novel invention, many variations and modifications will now be obvious to those skilled in the ant, and I prefer, therefore, to be limited not by the speci is disclosure herein but only by the appended claims.

I claim:

1. A hermetically sealed housing for a photoconductive element; said housing comprising a longitudinally symmetrical transparent tube having the ends thereof sealed; said photoconductive element being comprised of an at least partially tubular base member having a photosensitive outer surfacc; said photosensitive outer surface facing outwardly of said tube; said photoconductive element being contained within said tubular housing and having a terminal extending beyond the end of said housing; and securing means for securing said photoconductive element within said housing and for sealing the ends of said tube; said sealing means comprising a rigid transparent insulating medium filling the interior of said tube; said medium comprising an epoxy resin.

'2. A hermetically sealed housing for a photoconductive element; said housing comprising a longitudinally symmetrical transparent tube having the ends thereof sealed; said photoconductive element being comprised of an at least partially tubular base member having a photosensitive outer surface; said photosensitive outer surface facing outwardly of said tube; said photoconductive element being contained within said tubular housing and having a terminal extending beyond the end of said housing; and securing means for securing said photoconductive element Within said housing and for sealing the ends of said tube; said sealing means including at least one end plug of material scalable to the material of said transparent tube; said end plug having said terminal extending therethrough and being sealed to the end of said tube.

3. A hermetically sealed housing for a photoconductive element; said housing comprising a longitudinally symmetrical transparent tube having the ends thereof ealed; said photoconductive element being comprised of an at least partially tubular base members having a photosensitive outer surface; said photosensitive outer surface facing outwardly of said tube; said photoconductive element being contained within said tubular housing and having a terminal extending beyond the end of said housing; and securing means for securing said photoconductive element Within said housing and for sealing the ends of said tube; said photoconductive element comprising a cadmium-sulphide element; said housing being filled with a transparent medium.

4. A hermetically sealed housing for a photoconductive element; said housing comprising a longitudinally symmetrical transparent tube having the ends thereof sealed; said photoconductive element being comprised of an at least partially tubular base member having a photosensitive outer surface; said photosensitive outer surface facing outwardly of said tube; said photoconductive element being contained within said tubular housing and having a terminal extending beyond the end of said housing; and securing means for securing said photoconductive element Within said housing and for sealing the ends of said tube; said photocondnctive element comprising a cadmium-sulphide element having a conductive terminal region running along the axial direction of the tubular arranged element; said terminal being electrically and mechanically connected to said conductive terminal region.

5. A hermetically sealed housing for a photoconductive element; said housing comprising a longitudinally symmetrical transparent tube having the ends thereof sealed; said photoconductive element being comprised of an at least partially tubular base member having a photosensitive outer surface; said photosensitive outer surface facing outwardly of said tube; said photoconductive element being contained within said tubular housing and having a terminal extending beyond the end of said housing; and securing means for securing said photoconductive element within said housing and for sealing the ends of said tube; said photoconductive element comprising a cadmium-sulphide element; said terminal having an inner large cross-section conforming to the shape of said element at the region at which said terminal is connected to said conductive terminal.

References Cited in the file of this patent UNITED STATES PATENTS 2,544,554 Holmes Mar. 6, 1951 2,660,653 Berkelhamer Nov. 24, 1953 2,776,357 Porath Ian. 1, 1957 2,918,584 Edsberg et a1 Dec. 22, 1959 FOREIGN PATENTS 314,838 Great Britain July 3, 1959 

1. A HERMETICALLY SEALED HOUSING FOR A PHOTOCONDUCTIVE ELEMENT; SAID HOUSING COMPRISING A LONGITUDINALLY SYMMETRICAL TRANSPARENT TUBE HAVING THE ENDS THEREOF SEALED; SAID PHOTOCONDUCTIVE ELEMENT BEING COMPRISED OF AN AT LEAST PARTIALLY TUBULAR BASE MEMBER HAVING A PHOTOSENSITIVE OUTER SURFACE; SAID PHOTOSENSITIVE OUTER SURFACE FACING OUTWARDLY OF SAID TUBE; SAID PHOTOCONDUCTIVE ELEMENT BEING CONTAINED WITHIN SAID TUBULAR HOUSING AND HAVING A TERMINAL EXTENDING BEYOND THE END OF SAID HOUSING; AND SECURING MEANS FOR SECURING SAID PHOTOCONDUCTIVE ELEMENT WITHIN SAID HOUSING AND FOR SEALING THE ENDS OF SAID TUBE; SAID SEALING MEANS COMPRISING A RIGID TRANSPARENT INSULATING MEDIUM FILLING THE INTERIOR OF SAID TUBE; SAID MEDIUM COMPRISING AN EPOXY RESIN. 